Unusual wr400 valve cover wear?

Let me start by saying that I have a 1998 wr400. I was recently checking my valve clearance and I noticed this worn line on my valve cover that I don't recall being there before. I'm pretty sure it was dug into the plastic section before, but I assumed that was normal.

For your reference, I installed a rebuilt head a couple hundred miles ago, and the first time I checked the valves, I wanted to be sure my timing was spot on, and I ended up taking off the tension-er. When it was reinstalled I was sure to re-torque everything to spec. I do not recall the worn section on the valve cover as being there before. The only thing I do not torque is the valve cover itself which I can highly suspect is the cause of this problem, should I just not tighten it up as much?

I have also heard these bikes have poorly designed tension-ers that are prone to failure, is there an aftermarket replacement that works better?





New cam chain and tensioner when you did the rebuild? If I were to venture a guess, the chain is plapping about.

I did not replace the tensioner. Is there a manual tensioner I can "set and forget?"

Yup, there are. You still need to check the adjustment like once a year but, it will never fail like an OEM spring one can and does.

When the OEM tensioners go, they tend to wear the chain due to too much tension, a worn chain whips (and eventually, can jump a tooth).

Thanks, you've been tons of help. I know these are the questions people hate answering, but where can I find a manual tensioner? The manual/mechanical tensioners I've found on here and google don't seem to be available for the WR, and the threads I've looked up say they don't make them because they aren't needed for the wr as the OEM tensioner should outlast the bike. Should I buy a new chain and tensioner? Or just one or the other?

Thanks again,


Contact TT moderator Eddie Sisernos, he can hook you up. I think APE makes one for your bike. I use manua ones on all my bikes. One less thing to worry about. And they all fail, anyone who says otherwise is a prayer.

At the least, I'd replace the chain. Normally, it is swapped out every time the head is pulled at a minimum. Cheap insurance.

Thanks, I emailed him. The head stays on for chain replacement correct? I just bought all new head hardware and would hate to replace it again.

Also, what would cause such an exact line in the valve cover? I would think that if the chain was popping up like that, the scrape would be wider. I suppose this also explains some of the metal in my oil :ride:

Yup, head stays put. You pull the flywheel off, valve cover and cams. Job takes like 30 minutes to do, tops.

I figured I'd keep this thread updated incase someone searches for it later down the line. I was emailing back and forth with Eddie and he thinks that one of the plates on my cam chain has popped loose and is what has caused the scratches. I will confirm this when I get home, and if that is the case I will consider myself lucky that it was caught before my chain exploded


Yup, head stays put. You pull the flywheel off, valve cover and cams. Job takes like 30 minutes to do, tops.

I'll be pleasantly surprised if the chain can be replaced without damaging it without pulling the head. If I remember the layout correctly, the threaded tip of the crank sticks out too far and it would take some serious forcing/bending of the chain to get it around the tip (if dropped from above).

To the OP - let us know how it goes.

Yes, it is a little tricky doing it with an assembled motor but not too hard and not stressful on the chain. You put it over the crank in a lump and then fish it up the cavity.

Found my problem thanks to Eddie!

Three broken links all within a couple inches. Was it just an old chain? Is there a bigger problem I should worry about? You can the middle links are broken and can turn up which would gouge out the valve cover.



Ordering a chain and APE manual tensioner tomorrow. Combined with the re-shimming of the exhaust valves, it should hopefully quiet things down and perform better.

Edited by nnamssorxela

If that is the case, then where does the claim that the tensioner "backs off" under rapid throttle closure come from? I want a dependable bike that doesn't allow my cam chain to slap around and possibly skip teeth. If the oem tensioner will work then there is no need for me to spend 65 to replace it. At the same time I don't mind spending the money if it will be more dependable in the long run. The chain guides are pretty chewed up from the broken links on the chain digging them out, so I need to pull the head to replace them anyway. I'm open to suggestions.

Ordered the parts yesterday. I'll post up if I find anything unusual.


So I've been thinking. I have no idea how likely or implausible this is but here goes. I decided to check my valve clearances because the motor had been sounding especially noisy, even for a WR. When I checked the valve clearance, the intake was still spot on from the last time I checked if I remember correctly, but the exhaust had widened a couple sizes. I haven't sat down and done any math to see how much clearance is added by each tooth, so that might completely falsify what I think might have happened. I'm thinking that due to chain wear (and therefore added length), or maybe a malfunctioning tensioner, my chain was allowed to slap up and skip a tooth on the exhaust cam and when it came down it broke the 3 links as the cam caught the chain again, also causing the clearance to widen considerably on the exhaust cam. Again, I'm sure I'm overlooking something elementary, so feel free to point it out as I am quite curious.


If you measure clearance at the heal of the cam, a few degrees either way will not make a difference, in fact if ou go too far, you will get a decreased clearance value.

Valves typically tighten, not loosen. You need to investigate further.

Is it plausible that I was actually shimmed correctly, but that I had so much timing chain slack that it allowed some play in my cams? Also, I thought some of you might like the pictures of my chain guide...


The orange pencil is flat across.


I pulled the chain out the other day and I was surprised to find out how stiff that it was compared to the new one.

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